Effects of Different Rootstocks on Leaf Early Chlorosis Symptoms and Vegetative Growth of Grafted Japanese Quince (Chaenomeles japonica) Under Greenhouse Conditions

Iron chlorosis is a major problem in the cultivation of Japanese quince (Chaenomeles japonica). The chlorophyll content, green leaf production capacity of Japanese quince, and quality of the tree's appearance decrease in the landscape because of leaf chlorosis in alkaline soils. The use of tolerant rootstocks on calcareous soils is recommended as the best way to overcome the harsh conditions of alkaline soils. The objective of the present research was to explore vegetative growth, leaf chlorosis symptoms, and graft compatibility or incompatibility among different rootstock combinations and to determine appropriate Japanese quince rootstock for use in landscape establishment in alkaline soils. This experiment was conducted from March to May 2021 in the greenhouse of the Agricultural and Environmental Science at Arak University, Iran. Japanese quince grafted on four rootstocks, including seedling apple (Malus domestica cv. Gami Almasi), dog rose (Rosa alba), Japanese quince (Chaenomeles japonica), and pyracantha (Pyracantha coccinea). The grafting indices and morphophysiological characteristics were evaluated after 70 days. The traits that were measured were grafting success, number of activated buds on each scion, branch length, leaves number, chlorosis and necrosis sign, root volume, length of the longest root, fresh and dry weights of shoots and roots, chlorophyll and carotenoids of leaves, and phosphorus, potassium, iron, manganese, and nitrogen content of leaves. Japanese quince grafted on pyracantha rootstock showed higher vegetative growth of shoots and chlorophyll content than Japanese quince grafted on other rootstock. A significant positive correlation was found between phosphorus concentration and rootstock fresh weight and dry weight, scion dry weight and iron concentration, phosphorus concentration of the scion, root volume, carotenoid and iron concentration of the scion, iron and potassium concentration of the scion, and potassium and nitrogen concentrations. In addition, the manganese concentration of the scion was negatively correlated with the fresh weight of the rootstock, scion dry weight, chlorophyll content, and potassium concentration. Hence, pyracantha can be an excellent rootstock for Japanese quince because it induces a higher tolerance to leaf chlorosis. This confirms the ability to use this rootstock in large-scale commercial Japanese quince grown under alkaline conditions.